Orientadora: Profa. Dra. Paula Toshimi Matumoto Pintro

Data da Defesa:26/03/2021


INTRODUCTION.Used for the commercial productionof tannins, charcoal and in the paperindustry, Acacia mearnsiiDeWild trees naturally producean exudate(gum), which is notapplied industrially, and is considered acrop residue. Recent studies show that the gum Arabicobtained from A. mearnsiihas achemical composition similar to the commercial gum Arabic,which areobtained fromthe species Acacia senegaland Acacia seyal. A. mearnsiigumis acomplex, hyper-branchedamphiphilic heteropolysaccharide, composed of galactose, arabinose,rhamnose, uronic acids and proteins with physicochemical characteristics that allow itto act as afood stabilizer/emulsifier. Gums obtained from trunk exudate and treebranches areamongthe commercial hydrocolloids commonly used by the food industry. When added to foodpreparations, gumsgive the product athickening effect, stabilizefoams, emulsionsand dispersions, inhibitsyneresisand crystal formation (iceandsugar)and control the releaseofflavors. Considering the technological applicationsof gums, theirusein the production of dairy products, such as icecream and processed cheese(products formed by emulsions), can contributeto the development of new products with different technofunctional characteristicsthan traditional products.AIMS.Theobjectiveofthis studywas to characterizethepolysaccharidesfrom A. mearnsiigum, to evaluatethesafety of theirusebycytotoxicological tests andtheir stabilizing potentialbyphysicochemical, rheological andtextureanalyzes,in dairy products thatformed byemulsions,such as ice cream and processed cheese.MATERIALAND METHODS.Thepolysaccharides fromA.mearnsiiwereobtained after aqueous extraction of theraw gum, collected from trees grown in the stateof Rio Grandedo Sul, Brazil(kindly provided by thecompanySetaSA). Polysaccharidesfrom A. mearnsiiwerecharacterized by nuclearmagneticresonance(NMR) analysis and Fourier transform infraredspectroscopy (FTIR). Thecytotoxicity of A. mearnsiigum and cellproliferation analyzes wereperformed on Balb/3T3 cells (non-tumor murinefibroblasts) and HepG2 (humanhepatocarcinoma). A. mearnsiigum and the commercial gumsof A. senegaland A. seyalwereused as stabilizers in icecream formulations, AMS-icecream with A. mearnsiigum,ASG -icecream with A. senegalgum and ASY -icecream with A. seyalgum. Icecreams wereevaluatedfortheir physicochemical, textureand rheological properties. A.mearnsiigum was used as astabilizer in low-fatprocessed cheeseformulations. Processed cheeses had theirfat percentagereduced by 50%and wereadded with different concentrations of gum. Sixformulations wereprepared: STAN -standard processed cheese; CONT -low-fatprocessedcheesewithoutA.mearnsiigum;PC125 -low-fatprocessed cheeseand0.125%A. mearnsiigum;PC250 -low-fatprocessed cheeseand 0.250%A. mearnsiigum; PC375-low-fatprocessed cheeseand0.375%A. mearnsiigum and PC500 -low-fatprocessed cheeseand 0.500%A. mearnsiigum. Thechemical composition,color,physicochemical, textural andviscoelastic properties of processed cheeses wereanalyzed.RESULTSAND DISCUSSION.A. mearnsiigum presented acarbohydrate compositionsimilar to commercial gum Arabic.Galactose,arabinose, rhamnose,aliphaticgalactoproteins, uronicacid, arabinogalactan proteins and pyranoserings wereidentifiedby NMR and FTIR. Theresults obtained in cytotoxicity testsshow that theuseof A. mearnsiigum issafein itsvarious applications, sincethe treatment of the gum did not affect cellproliferation nor wastherealossof cellviability of both tested celllines. Icecream prepared with A. mearnsiigum (AMS)showed higher viscosity than with commercial gumArabic. Protein present in theA.mearnsiigum provided an increasein colloidal particles of theicecream (denaturedproteins, caseins, etc.) and increased viscosity. Themolecularinteractions between mixturecomponents increased the hardness, reducing the overrun of AMS. AMS and ASY show resistancewhen subjected to ashear stress (higher shear rates to initiate the flow/deformation), indicating the presenceofamorestructured and robust three-dimensional network dueto molecular interactions, reducing the tendency to melt. Theobservation ofasmaller hysteresisareaof AMS allowed to conclude thatits structureis recovered morequickly than othersamples preparedwithcommercial gumArabicwhensubjected to a deformation;and itis a morestablesystem -which is an importantproperty of icecream to beresistant to adverseconditions during the production chain (from processing conditions to consumption). Low-fat processed cheeses weremadewith and withoutthe addition of A. mearnsiigum, and showed a40%reduction in calories. Thegum inclusion in processed cheesesincreased the carbohydratesconcentration, and PC500 samplehad protein content similar to STANsample. Theyellowcolor of processed low-caloriecheeses was affected, and the gum inclusionmadethe yellowingindex of processedcheeses intermediatein relation to STAN and CONT. Thetextureprofileanalysis showed that the low-fatprocessed cheesesweresofter and morespreadablethan STAN. In thefrequencysweep, low-fat cheeses processed presented smaller elastic (G’) andviscous (G”) modulus thanSTAN; but the increasein gumconcentration raised the values of G’and G”according tofrequencyincrease, possibly dueto interactions between protein aggregates and the gumin the continuous phase, improving the elastic and viscous propertiesof PC125, PC250, PC375.PC500 showed higherG’and G”among low-fat processed cheeses and viscoelastic behavior (same behavior ofSTAN), probably dueto the highergumconcentration, which increases thenumberof molecularinteractions between the constituents, helping in their emulsification, making the processed cheesestronger andwith aharderand less spreadable consistency. Theoscillation thermometry showed that milk fat has an influenceonthe viscoelastic characteristicsof processedcheeses. STANshowedelasticbehavior throughout thetemperaturescan and thesamples with low fat content showed viscoelastic behavior dueto possible interactions betweenprotein-protein andprotein-carbohydrate, mainly occurring at temperatures above45 °C. STANshowed changes in viscoelastic properties dueto the meltingand solidification of milk fatduring the temperaturevariation of the cycles. Processed cheeses with low fat content showed viscous behavior throughout the temperaturerangetested in the cycles. In allprocessed cheeses,the data werereproducible, the behavior observedin the first temperaturecycle, was repeatedin the second. Themaintenanceof the viscous behavior of processed cheeses with low fat content shows that even after variations in temperature, the processed cheesesmaintain asofttexture and preserve their spreadability.CONCLUSIONS.A. mearnsiigum is safeto usein food process;however, moretoxicity tests need to becarried out.Theicecream madewith A. mearnsiigum had technological characteristics (physicochemical and rheological) relevant to industrial processes and thecommercialization of theproduct. Fat reduction and the inclusion of A.mearnsiigum influencethe mechanical and textural properties ofprocessedcheeses. Thelow-fat processed cheeses and with A. mearnsiigumaddition becamesofterandmorespreadable than thestandard sample,and provedto bestablewhen subjected to temperaturevariation cycles. Theresults show that mearnsiigum can beused by the food industry as astabilizer and can become asourceof income and not a residue in the production chain of A. mearnsii.

 Keywords:hydrocolloids, gums, icecream, processed cheese, textural properties, rheological properties.


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